Instrument.



J. A. CLARKE.

INSTRUMENT.

APPLICATION FILED APR. 18, 1916.

WITNESS I IV I/ E /V TOR fagiaxaizdfw /af/fe/ ATTORNEYS Patented Apr. 10, 1917.

JAMES ALEXANDER CLARKE, OF DEVON, PENNSYLVANIA.

INSTRUMENT.

Specification of Letters Patent.

Patented Apr. 10, 1917.

Application filed April 18, 1916. Serial No. 91,929.

To all whom it may concern:

Be it known that I, J AMES ALEXANDER CLARKE, a citizen of the United States, and a resident of Devon, in the county of Chester and State of Pennsylvania, have invented certain new and useful Improvements in Instruments, of which the following is a specification.

My invention relates to mechanical means for trisecting any given angle, and the object thereof is to provide an instrument of precision for accomplishing this result without the need for any calculation, which is instantaneous in results, which may be used P by any unskilled person by following very simple directions, and which is composed of few parts not likely to get out of order and comprise a very inexpensive structure.

My invention is fully described in the following specification, of which the accompanying drawings form a part, in which like characters refer to like parts in each of the views, and in which Figure 1 is a plan view of my instrument, ready for use;

Fig. 2 is an enlarged section taken on the line 22 of Fig. 1; and

Fig. 3 is an enlarged section taken on the line 33 of Fig. 1.

Referring to the drawings, 4 represents a base bar provided with a longitudinal slot 5 and carrying, at one end, a fixed pivot 6 for a side bar 7 in turn carrying a fixed pivot 8 for a similar side bar 9 in turn pivoted at 10 to a leg bar 11, the pivot 10 being slidable in the slot 5 of the base bar 4, and the outer end of said leg bar 11 is provided with a fixed pivot 12 for an arm 13 carrying a pin 14 also slidable in the slot 5.

Each of the side bars, the leg bar, and the arm, is cut away along one side to form an edge in register with a line passed through the axis of corresponding pivots, whereby the instrument may be applied to an angle which it is desired to trisect, and it will be noted that the pivots 6 and 8, 10 and 12, 8 and 10, and 12 and pin 14, are equidistant from each other.

Having given an angle whichit is desired to trisect, the pivot 8 is placed at the vertex of the angle, the sidebar 7 arranged along one side of the angle so that the line of the angle coincides with a line drawn through the axes of the pivots 6 and 8, the pivot 10 being then moved along the base bar 4 until the side bar 9 coincides with the other side of the angle, the side arms 7 and 9 being firmly held in these positions.

The pin 14 is now slid along the base bar 4 until the arm 13 coincides with a line drawn through the axes of the pivots 8 and 12, this tending to swing the leg bar 11 on the pivot 10, as into the dotted position shown, and this line, bearing the character 15, divides the angle into two portions, the one on the left being one-third and the one on the right being two-thirds of the given angle.

When this line is struck, the length of the arc 16, between the pivot '10 and the point where an arc of the angle is intercepted by the line 15, enables the two-thirds portion to be bisected, thus trisecting the angle.

This may be accomplished in an instant and without mental efiort, regardless of what the given angle may be, and accurately, and the instrument itself is so inexpensive as to permit its possession by all mathematicians, engineers, draftsmen, students, and others.

The proof hereof may be given as follows, with the parts in the positions indicated by dotted lines and we have Having fully described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. An instrument of the class described, comprising a base bar provided with a longitudinal slot, a pivot at one end of said base bar, a side bar mounted on said pivot, a second pivot on the outer end of said side bar, a supplemental side bar mounted on said second pivot, a third pivot carried by said supplemental side bar and slidable in said slot, a leg bar mounted on said third pivot, a fourth pivot at the outer end of said leg bar, an arm mounted on said fourth pivot, and a pin carried by said arm and slidable in said slot.

2. An instrument of the class described, comprising a base bar provided with a longitudinal slot, a pivot at one end of said base bar, a side bar mounted on said pivot, a

second pivot on the outer end of said side bar, a supplemental side bar mounted on said second pivot, a third pivot carried by said supplemental side bar and slidable in said slot, a leg bar mounted on said third pivot, a fourth pivot at the outer end of said leg bar, an arm mounted on said fourth pivot, and a pin carried by said arm and slidable in said slot, said first and second pivots, second and third pivots, third and 10 fourth pivots, and fourth pivot and pin, being equidistant from each other.

JAMES ALEXANDER CLARKE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. C. 

